At the height of Telecom's problems with its XT mobile network and access to 111 emergency services, the besieged company kept the public in the dark about faults affecting almost half the country.

One fault required a technician to be dispatched to the Otago town of Lawrence, where he sat in the out-of-order phone exchange with his own mobile phone to call services about any 111 emergencies.

That same morning, an unrelated and previously unpublicised XT outage meant 16 South Island emergency calls failed to connect - six of which were later discovered to have been genuine emergencies.

Now, communications minister Steven Joyce says he will consider imposing sanctions on Telecom for the 111 outages. He has commissioned urgent reports into the problems.

The extent of those problems can be revealed after the Herald on Sunday used the Official Information Act to obtain documents detailing simultaneous outages on March 18 with XT calls in the South Island and a microwave transmitter crash that cut Lawrence off from the rest of the world.

The revelations come as Telecom chief executive Paul Reynolds fronts television ads trying to salvage the problem-plagued network.

In the advertisements, Reynolds asks customers to "give XT another shot now it is working exactly as it should have done".

But emails between Telecom and the minister's office show the communications company was determined to keep the March 18 XT outage quiet.

Emails show the minister was kept informed of the problems.

On the morning of March 18, an unidentified Telecom staffer advised the minister's office by email: "We have decided not to proactively make a release at this stage."

The Telecom staffer said the crash in XT services was caused by "the planned installation of a software patch which had unplanned consequences".

Telecom spokesman Mark Watts said the company did not inform the public of the problem because there was no need: "This fault occurred in the very early hours of the morning and was restored before 4am."

He said 16 emergency calls made by XT mobiles failed to be connected during the crash, but were followed up by 111 staff.

In situations such as Lawrence, technicians were sent to answer 111 calls: "Someone literally sits in the exchange building and answers the phones," Watts said.

But Joyce said the decision to not publicly disclose the March 18 faults was Telecom's.

He was frustrated at the 111 system: "We have very little ability to impose sanctions, and also little direct visibility into how these issues are being handled. We're working on that with urgency."

He said several reports were being prepared on the matter and the Government was considering introducing fines for operators who failed to provide a reliable 111 service.

"Sanctions are one option," he said.